SANTA CLARA — Almost every time Donte Whitner looks at rookie Eric Reid he's reminded of what it was like to be a safety selected in the first round competing for a starting spot.

Whitner, San Francisco's savvy strong safety, had little time to adjust to NFL life. After being taken eighth overall by the Buffalo Bills in 2006, he had quite the Week 1 opponent: Tom Brady and the New England Patriots.

Reid, the former LSU standout the 49ers drafted at No. 18 after trading up to get him, is hoping to start against Aaron Rodgers and the Green Bay Packers in the regular-season opener Sept. 8. And when San Francisco hosts Denver in his first preseason game Thursday night, Reid might even get a few snaps against another former NFL MVP: Peyton Manning.

"I think that would be great," Whitner said Monday. "I think that would be great for him to get experience in all four [preseason] games because you can go out and make mistakes in these games, get your first NFL game action and not cost us anything. The only thing it might cost you is a little confidence if you get beat."

While Reid is getting his turn with the first-team defense, he has yet to win the starting job.

The competition to replace All-Pro free safety Dashon Goldson — who signed a free agent deal with the Tampa Bay Buccaneers — has been among the closest in camp. C.J. Spillman, Trenton Robinson and Craig Dahl all have spent time starting in practice, giving way in the rotation this week to the rookie.

"Right now it's a battle," defensive coordinator Vic Fangio said. "It will sort itself out. The one good thing about training camp, we get a lot of reps."

In college, Reid played a 4-3 scheme at LSU, while San Francisco uses a 3-4 alignment. Reid said the concepts are the same, but the responsibilities fall to different people — and can change after the ball is snapped, which never happened at LSU.

"The biggest adjustment is this is a job," Reid said. "The coaches have families to feed. Other players have families to feed. So their job is kind of dependent on you. So you want to make sure you do what you have to do to help those guys out to win games."